The French forward came off the bench to net in his second consecutive Premier League match.

Eric Bailly had given United the lead on the stroke of half-time before the Red Devils added three goals in four minutes late on.

Romelu Lukaku followed up his impressive home debut by netting before Martial and Paul Pogba completed the rout.

Mourinho said: "Happiness in our play. It happened to me so much with my teams, you winning 1-0 and you can can concede. There was no need to close the door, just let the horses run freely.

"Anthony Martial is working hard. He is confident. The French language connection is there to help him a lot and get to the level we know he can be because the potential is huge."

Player Ratings: Manchester United at Swansea

MANCHESTER UNITED hammered Swansea 4-0 today, but how did each player get on?

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Manchester United FC

Manchester United: Team average - 7.71

“Anthony Martial is working hard. He is confident. The French language connection is there”

Manchester United boss Jose Mourinho

Mourinho also analysed the game and thinks United were good value for their lead.

He explained: "During almost 90 minutes, I don't say 90 because there was a moment when they had a chance and we lost a little bit the confidence. They were waiting with class, calm and consistency for the moment to kill the game.